1. Field of the Invention
The present invention relates to an image processing method, and more particularly, to a method for adjusting the color temperature of an image.
2. Description of the Prior Art
Color correction has been a standard step in photo processing for decades, and with the transition to digital imaging it has also proven necessary in image processing. Cameras do not record images according to the perception of human vision, but rather according to the physical properties of photosensitive chemicals or electronic circuits.
Accordingly, many models have been used to correct the color temperature of images. A common model is the “gray world” model, which assumes that in an image with sufficient color variety, the average color will be a uniform gray. The average color of the image, taken by summing each color component of every pixel and dividing by the number of pixels, is calculated, and all pixels are shifted by that amount to balance the image.
These models have several problems, first among them that images often do not balance out to gray. An image dominated by a red apple, a blue sky, or a green field will tend to throw non-dominant sections of the image out of balance as the color correction overcompensates. Lighting can affect the color balance of an image, as when a picture is shot under fluorescent light versus incandescent light. In some cases, the color of an object can actually be shifted to a different spectral region during correction, such as being shifted from blue to green.
An improved model for color temperature correction would be of clear benefit.